1. Field of the Invention
The present invention relates to a golf ball. More particularly, the present invention relates to an improvement in a dimple pattern of the golf ball.
2. Description of the Related Art
A golf ball flies with a backspin by hitting. The golf ball then drops and rolls over the ground, and comes to rest. A distance from a hitting point to a drop point is referred to as a carry. A distance from the drop point to a rest point is referred to as a run (or a roll). A distance from the hitting point to the rest point is referred to as a total distance.
A golf ball has a large number of dimples on a surface thereof. The dimple usually takes a circular plane shape. A non-circular dimple has also been proposed. In respect of an aerodynamic symmetry and the easiness of the manufacture of a mold, a circular dimple is a mainstream in golf balls put on the market.
The role of the dimples resides in one aspect that such dimples disturb an air stream around the golf ball during a flight, thereby causing a turbulent flow separation (which will be hereinafter referred to as a “dimple effect”). The separation of the turbulent flow causes a separating point of air from the golf ball to be shifted backward so that a drag coefficient (Cd) is reduced. The separation of the turbulent flow increases a differentia between the upper and lower separating points of the golf ball which is caused by a backspin. Consequently, a lift acting on the golf ball is increased. A reduction in a drag and an enhancement in a lift cause the flight distance of the golf ball to be increased. An aerodynamically excellent dimple promotes the separation of the turbulent flow.
Examples of the specifications to greatly influence the flight performance of a golf ball include a density of dimples (which is also referred to as a “surface area occupation ratio”) A golf ball having a high density is excellent in a flight performance. Various proposals for the density have been made. Japanese Laid-Open Patent Publication No. Sho 62-192181 has disclosed a golf ball in which dimples are densely provided in such a manner that a new dimple having an area which is equal to or more than a mean area cannot be formed. Japanese Laid-Open Patent Publication No. Hei 4-347177 has disclosed a golf ball in which dimples are provided very densely and the number of lands in which a rectangle having a predetermined dimension can be drawn is 40 or less. Japanese Laid-Open Patent Publication No. 2002-186684 has disclosed a golf ball in which a surface area occupation ratio and a dimple contour length satisfy a predetermined relationship.
Examples of other specifications to greatly influence the flight performance of a golf ball include a total volume of dimples. In the case in which the total volume is small, the trajectory of the golf ball tends to be high. On the other hand, in the case in which the total volume is large, the trajectory of the golf ball tends to be low.
Although a great carry can be obtained in a high trajectory, the speed of the golf ball is low during dropping so that a run is small. In the case in which the total volume is small, a total distance is insufficient. In a low trajectory, the run is great and the carry is small. Also in the case in which the total volume is large, the total distance is insufficient. In addition, in the case in which the trajectory is low, a variation in the carry is great.
Thus, the run is small in a golf ball having a great carry and the carry is small in a golf ball having a great run. The maximum demand for a golf ball of a golf player is a flight distance. In particular, the golf player attaches importance to a total distance obtained by hitting through a driver. It is an object of the present invention to provide a golf ball giving a great total distance.